1. Field of the Invention
The present invention relates to a mechanical seal, and, particularly, to a mechanical seal with a retainer holding two compression rings by engaging blocks and engaging with two rotating seal rings by a plurality of slide legs.
2. Description of the Related Art
Referring initially to FIG. 1, a conventional rotary machine such as a pump system has a shaft 9, which may be used to stir liquids contained in a housing such as a liquid tank. In rotating operation, the rotary machine functions as a stirring apparatus of the housing for example. The rotary machine generally includes a mechanical seal for keeping the stirred liquids within the housing.
Typically, the mechanical seal includes a gland 7 and a rotating assembly 8. The gland 7 permits extension of the shaft 9 and mounts the shaft 9 on equipments such as the said housing. The rotating assembly 8 is securely mounted on and rotated with the shaft 9 while being received in the gland 7. The gland 7 includes a shaft bore 70, a fluid inlet 71, and a fluid outlet 72. The shaft bore 70 longitudinally extends through the body of the gland 7 for the rotating assembly 8 and shaft 9 to pass through. The fluid inlet 71 and fluid outlet 72 both communicate the outside of the gland 7 and the shaft bore 70 for gas or a coolant to be guided into and out of the shaft bore 70 through the fluid inlet 71 and the fluid outlet 72. Besides, two stationary seal rings 73 are oppositely received in the shaft bore 70 at two ends thereof, and longitudinally sandwiched between the gland 7 and rotating assembly 8, with both of the stationary seal rings 73 being able to move longitudinally.
The rotating assembly 8 includes a retainer 81, a pair of compression rings 82, a pair of O-rings 83, a pair of rotating seal rings 84 and a shaft sleeve 85. The retainer 81, the compression rings 82, the O-rings 83 and the rotating seal rings 84 are mounted and assembled on an outer periphery of the shaft sleeve 85. There are a series of spring members 810 provided on each of two longitudinally opposite sides of the retainer 81 for bias forces of the spring members 810 to oppositely push the two compression rings 82 outwards relative to the retainer 81. Besides, a plurality of pins 811 are also sandwiched between the retainer 81 and the compression rings 82 for preventing the compression rings 82 from revolving about the shaft 9. Two side surfaces of each compression rings 82 are respectively in contact with the corresponding spring members 810 and the corresponding rotating seal ring 84. The O-rings 83 are disposed between the compression rings 82 and the rotating seal rings 84 for providing sealing effects therebetween. Each of the rotating seal rings 84 closely abuts one of the stationary seal rings 73. Furthermore, the shaft sleeve 85 is mounted on the shaft 9 and rotated therewith.
When the shaft 9 rotates, the stationary seal rings 73 in the shaft bore 70 of the gland 7 elastically abut against the rotating seal rings 84 of the rotating assembly 8. In long-term use, there are abrasions occurring between the stationary seal rings 73 and the rotating seal rings 84 of the rotating assembly 8. The bias forces of the spring members 810 ensure no gap existing between the stationary seal rings 73 and the rotating seal rings 84 by successively pushing the rotating seal rings 84 through the corresponding compression rings 82. Consequently, the bias forces of the spring members 810 can reduce the possibilities of liquid leakage in the interior of the mechanical seal.
The conventional mechanical seal has several drawbacks in manufacture. In the installing process, the spring members 810 must be disposed between each side of the retainer 81 and the corresponding rotating seal rings 84 without any positioning member before the whole rotating assembly 8 is completely fixed on the shaft 9. The primary problem in such a structure is the difficulty in assembling or maintaining due to the fact that the spring members 810 may be easily fallen off from the retainer 81. Disadvantageously, this may result in a low efficiency in assembly of the above-mentioned elements of the mechanical seal. Moreover, convenience in assembly is especially important for repair or replacement of the rotating seal rings 84 due to the said abrasions thereof.
Another problem naturally occurring during use of such a mechanical seal is due to the fact that liquids contained in the housing may permeate through a clearance existing between the compression ring 82 and the rotating seal rings 84. With the structure shown in FIG. 1, because the spring members 810 for pushing the rotating seal rings 84 at two sides of the retainer 81 are isolated, there is no assistant effect provided by the spring members 810 to prevent the compression rings 82 from revolving about the shaft 9. In this circumstance, the liquid pressure can press the O-ring 83 and the compression ring 82 to be moved backward to the retainer 81, and thus can further compress the spring members 810 to be retracted. Consequently, the rotating seal rings 84 cannot exactly abut against the corresponding stationary seal rings 73. Disadvantageously, the possibility of leakage in such a mechanical seal is increased.
Another conventional mechanical seal in U.S. Pat. No. 5,375,853 and titled “SECONDARY CONTAINMENT SEAL” discloses a retainer with a cylindrical outer circumferential and an inner wall, and an annular disk element with several apertures is arranged along a central portion of the inner wall. Therefore, a plurality of springs can be inserted in the apertures and sandwiched between a pair of discs disposed on two sides of the annular disk element, with the said springs oppositely pushing two rotating seal rings to respectively abut two stationary seal rings through the said pair of discs. However, in order to retain the discs and rotating seal rings within the retainer, there should be an internal groove adjacent to each end of the retainer for receiving a snap ring with a radially extending wall. As a result, the invention disclosed in the said cited patent provides a complex structure and an assembly process that are still inconvenient for processing the repair or replacement of the rotating seal rings. Furthermore, in operation, the retainer of this cited structure has to suffer a large torque and a revolving movement of the discs. Besides, still another conventional mechanical seal disclosed by U.S. Pat. No. 3,888,495, titled “DUAL-COOLED SLIDE RING SEAL,” provides a structure similar to the last cited patent and also has the same problem of inconvenience in assembly.
Another US patent titled “SELF-CONTAINED ROTARY MECHANICAL SEALS” and U.S. Pat. No. 4,213,618 shows another conventional mechanical seal mounted on a shaft for rotating therewith and including a lug holder, a plurality of lugs, a plurality of belleville washers, a contact washer, and a carbon seal washer. The lug holder is radially fixed around the shaft, with the lugs extending from the lug holder and parallel to the shaft. The belleville washers are radially surrounded by the lugs and axially compressed between the lug holder and the contact washer to create a spring force urging the carbon seal washer forwards into abutting against a seal seat. Regarding to this conventional invention, what is characterized is that a plurality of tines extending from the lugs in a direction perpendicular to the lugs and concentric to the shaft is provided while several shoulders radially extend from the carbon seal washer. Besides, the shoulders are dimensioned for engagement with the lugs and tines. In detail, a distance of a gap between two adjacent tines of two different lugs is not smaller than a length of the shoulder, so that the shoulder can pass through the gap and received between the said two different lugs. Although convenience in assembly for mechanical seal is improved by this conventional invention, the belleville washers and contact washer are still easy to fall out of the space defined by the lugs once the carbon seal washer is removed. And this is inconvenient for repair or replacement of the carbon seal washer as well. Furthermore, because the carbon seal washer directly abuts against the tines, the shoulders may be easily damaged due to axially pushing force of the belleville washers. Hence, there is a need for a further improvement over the conventional mechanical seal.